Dispersion Of Light Assignment Help

Dispersion Of Light

In this particular aspect of Physics we will discuss about another most important aspect of Optics which is known as dispersion of light. Dispersion of light is the phenomenon of splitting of a beam of white light into its constituent colors on passing through a prism. The band of seven colors so obtained is called the (visible) spectrum. The order of colors from the lower end of the spectrum is Violet (V), Indigo (I), Blue (B), Green (G), Yellow (Y), Orange (O), and Red (R) and can be recollected by the word VIBGYOR.

different colors turn through different angles on passing through the turn different angles on passing through the prism. Violet color deviates through maximum angle and red color deviates through the minimum angle.

Cause of dispersion

Each color has its own characteristic wavelength (λ). According to the Cauchy’s formula, refractive index (µ) of a material depends on wavelength (λ) of light as

µ = A + B/ λ 2 + C/ λ 4 + (1)

Where, A, B, C are constants.

Therefore, µ of material of prism is different for different colors.

For prisms of small refracting angle, we have shown that angle of deviation is

δ = (µ - 1) A

As µ of prism is different for different colors, therefore, different colors deviate through different angles on passing through the prism. Hence they are seen as separate. This is the cause of dispersion.

As, λviolet < λred

Therefore, µviolet > µred

Hence, δviolet > δred

i.e. max. deviation is of violet color. That is why violet color is at the lower end of the spectrum and red color is at the upper end.